Guest editorial

Abstract

The Eighth International Workshop on Foundations of Object-Oriented Languages (FOOL 8) was held on January 20, 2001, colocated with the ACM Symposium on Principles of Programming Languages in London. Kathleen Fisher chaired the program committee. Six contributed papers were presented. After the workshop, extended versions of three were solicited for this special issue of TOPLAS ; the two articles that were ultimately submitted were reviewed, revised, and accepted following standard TOPLAS procedures.The special issue opens with Type-Preserving Compilation of Featherweight Java by Christopher League, Zhong Shao, and Valery Trifonov. The goal of the authors is to establish a foundation for certifying compilation of Java-like class-based languages. To this end, the authors give an encoding of core Java features in a typed intermediate language suitable for use within a type-preserving compiler. Because of its intended use, the authors focus on developing an efficient encoding. They show that the type erasure of their implementation matches the standard vtable self-application semantics of message sending.The authors use Featherweight Java (FJ), which models the core features of Java, as their source language. Their translation targets a variant of F ω , already implemented as part of the SML/NJ compiler, using its row polymorphism and existential and recursive types to encode FJ. The authors show that the translation from FJ to their target preserves types.In the issue's second article, More Dynamic Object Reclassification: Fickle II , Sophia Drossopoulou, Ferruccio Damiani, Mariangiola Dezani-Ciancaglini, and Paola Giannini explore the issue of dynamic reclassification, by which an object changes its class membership at runtime while retaining its identity. This ability helps model real-world situations where an object has different roles over time---for example, a person who is first a student and then graduates to become a teacher.The authors focus their study on the design of a language, Fickle II , which extends an imperative, typed, class-based, object-oriented language with a reclassification operation. To specify the behavior of their language, the authors give an operational semantics. They then develop a type and effect system and show that the type system is sound, in the sense that a well-typed program cannot get stuck under the operational semantics.We would like to thank our colleagues who served on the FOOL 8 program committee and those who participated in the anonymous reviewing process for TOPLAS . Their efforts contributed greatly to the quality of this special issue.